So what is actually Singapore's official policy here? Does the official policy differ from the actual policy? I know that first-generation PR's are required to register for NS. Has any of them ever been required to actually serve it? Also, can an excemption from NS be revoked (if, say, Indonesia suddenly declares war on Singapore)? Also, does Singapore take it into consideration at all that it's illegal according to my home country's laws to register for NS in another state? Finally, are there any sources on the web which clarify this issue, instead of just repeating the Government's ambiguous statements?
I find their statement problematic because if all first-generation PRs truly are exempted, then why not state that? So either, they want to be able to ask non-PTS PRs to join the army in some hypothetical situation, or this is a symbolic law.
Yes, you can be required to undergo NS. In fact, Family Ties 1st Gen PR may be given less exemptions in the future, but not necessarily doing actual NS but maybe in some other form like some sort of community service.
Most are given waivers but the waiver can always be rescinded if necessary. That's the chance you take. If you become a 1st Gen PR and say you are only in your early to mid 20's there is a good likelihood of being called up, but if you are over say 26, the chances are slim. Of course, should there be an emergency, e.g., confrontation with Malaysia or Indonesia, then yes, there will be always a provision to allow for any waivers to be called in. Those in the PTS or Investors are only given PR because of what they can bring to Singapore therefore it would make no sense to have them taken away from that which was the ONLY reason for them getting PR in the first place.
However, if you come as the spouse of a Singapore girl, they figure if you can play you can pay if necessary. First Gen PR under the Family Ties are not "exempted" but waivered only. If you find it problematic, I would suggest you do not take up PR and you take your local bride elsewhere where you don't have to worry so much. But it is, however remote it is currently, a fact that will not go away. If you are over 30 the odds are very much against it except in wartime setting. But as a PR you would have already done a runner anyway, by the sounds of it.